Dual-mode equalization for digital mobile radio

Abstract

The performance of digital mobile radio systems when transmitting at over several tens of kbit/s severely degrades with the onset of fast fading multipath propagation. This paper proposes a dual-mode equalization (DME) method to overcome the degradation and experimentally verifies the effectiveness of the method. The new method uses decision feedback equalizers (DFEs) in two modes simultaneously, a normal mode, and a time-reversal mode, and selects the best equalization result. The time-reversal equalization mode improves the characteristics of equalization and adaptation in the non-minimum phase condition. It converts the nonminimum phase to the minimum phase condition by the time-reversal operation. Principles of dual-mode equalization, an algorithm for mode output selection, and timing problems are discussed in detail. Experiments demonstrate average BER performance in two-path and typical multipath environments. The proposed dual-mode equalization technique improves average BER performance by 2 dB Eb/N0.